JP3286014B2 - Coating method using coating composition having improved interlayer adhesion, and multilayer coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film using a coating composition having improved interlayer adhesion to a lower coating film, and a multilayer coating film.

[0002]

2. Description of the Related Art As represented by paints for automobiles, it is necessary to form a multi-layer coating film in order to protect the metal against corrosion and to have an aesthetic appearance. That is, an overcoat having a completely different composition and performance is often applied onto the undercoat. In this case, peeling of the coating film often occurs due to a decrease in adhesion between the undercoat coating film and the top coating film. On the other hand, a method of sanding the undercoating film to increase the adhesion to the overcoating film is often used. However, since the sanding step is added, productivity is deteriorated.

[0003] In the coating of automobiles, a thermosetting colored base coating is applied and, without baking, a thermosetting clear coating (hereinafter simply referred to as a clear coating) is applied on the base by so-called wet-on-wet. There is a method of painting and simultaneously baking and curing the colored base coat layer and the clear coat layer (this step is particularly called a two-coat one-bake method). However, in the automotive coating line, if a defect occurs in the coating film formed by this two-coat one-bake method, the base paint and clear paint are applied again by the two-coat one-bake method without sanding the coating film. Is being done.

When this is illustrated, a coating film as shown in FIG. 1 is formed. Since different materials are used for the base paint and the clear paint, adhesion between the first clear coat layer and the second base coat layer is poor, and peeling of the paint film may occur.

[0005] Phosphorus compounds have been used to improve adhesion. For example, US Pat.
No. 1,841 uses phosphoric acid or alkylbenzene sulfonic acid to improve adhesion, and the alkyl group bonded to the phosphoric acid or alkylbenzene sulfonic acid has 1 to 12 carbon atoms. Yes, and the adhesion to the undercoat film surface is not always sufficient. Also used here is free phosphoric acid, which is different from the phosphate ester compound of the present invention. In addition, the present invention does not include aromatic compounds in the sulfonic acid compound.

US Pat. No. 4,772,289 discloses that although a phosphoric ester having a polyether chain is used to improve the adhesion of a coating film to a leather product, the adhesion to the coating film surface is improved. Is not always sufficient and suffers from durability disadvantages based on ethers.

[0007] US Patent Nos. 4,839,403 and 4,
No. 801 628 uses a phosphoric acid ester containing a hydroxyl group consisting of phosphoric acid and an epoxy compound for improving adhesion. However, when this compound is used, the effect of adhesion to a metal surface is recognized, but the adhesion of a coated film surface is not always sufficient.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a method for forming a coating film using a coating composition having improved adhesion to an underlayer coating film by selecting a specific phosphorus compound or another compound, and a method for forming a multilayer film. It is intended to provide a coating film.

[0009]

That is, the present invention provides a cured coating film comprising a first base coat and a first clear coat formed on the first base coat on a base material, Applying a second basecoat without sanding the coating, applying a second clearcoat without curing the second basecoat, and then baking and curing both the second basecoat and the second clearcoat. In the method for forming a coating film, the first base coat and the second base coat are: (A) a film-forming resin, (B) a crosslinking agent for heat-curing the resin (A), and (C) a carbon number of 8 to 18 carbon atoms. Having a long-chain alkyl group and HLB
A phosphoric ester having from 3 to 12;
(C) a coating composition having improved interlayer adhesion, wherein the solid content of the component is 0.1 to 5% by weight based on the total solid content of the components (A) and (B). To provide a coating film forming method.

[0010]

[0011]

The present invention also provides a multilayer coating obtained by the above method.

The film-forming resin of the present invention is not particularly limited, and resins generally used for thermosetting paints can be used. Examples of such a material include an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, a urethane resin, or a combination of two or more of these resins. The solvent system of the coating material of the present invention may be either an aqueous solvent or an organic solvent, but in the case of an aqueous solvent, a group for water-solubilizing in the film-forming resin, such as a carboxyl group or an amino group. And by neutralizing these with a neutralizing agent, they can be dissolved or dispersed in water. Preferred resins include an acrylic resin and a polyester resin. Particularly preferred are 5 to 40% by weight of an amide group-containing ethylenic monomer [eg, (meth) acrylamide, N-methylacrylamide, N-butylacrylamide, etc.], an acid group-containing ethylenic monomer [eg, (meth) acrylic). Acids, maleic acid, itaconic acid, etc.] and other ethylenic monomers [e.g. (meth) acrylates such as methyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate;
Acrylonitrile; aromatic vinyl monomers such as styrene, etc.]. These resins generally have a hydroxyl value of 20-200, preferably 30-15.
Has zero. The hydroxyl group is considered to be a reaction point with the crosslinking agent.
The film-forming resin has a number average molecular weight of 1,000 to 50,
000, preferably 1,000 to 20,000.

In order to heat and cure the above-mentioned film-forming resin component (A), a crosslinking agent component (B) is required. Examples of such are: blocked polyisocyanate compounds, alkoxylated melamine formaldehyde condensates (melamine formaldehyde) or alkoxylated condensates with paraformaldehyde (e.g., methoxymethylol melamine, isobutoxylated methylol melamine, n
-Butoxylated methylolmelamine) and an alicyclic, aromatic or aliphatic epoxy compound containing two or more epoxies (e.g., Epikote 828, Epikote 1001, Epikote 1004, available from Shell Chemical Company,
Epolite 40E, Epolite 4 commercially available from Kyoei Yushi Co., Ltd.
00E, Epolite No. 1600, Epolite No. 7
21), and at least one of these is used.

The component (C) used in the present invention has 8 to 18 carbon atoms.
Is a phosphate ester having a long-chain alkyl group and having HLB 3-12. The alkyl chain has 8 to 18 carbon atoms.
If the number of carbon atoms is less than 8, the wettability to the coating film is reduced, and the adhesion is poor. On the other hand, when the number of carbon atoms exceeds 18, crystals of the compound are precipitated in the paint, which causes a problem. More preferably, it has 10 to 14 carbon atoms, the wettability becomes better, and the adhesion is improved. The HLB of the above compound is represented by a Griffin formula based on weight fraction: HLB = 20 (MH / M) [where MH is the molecular weight of the hydrophilic group portion, and M is the molecular weight of the activator]. The molecular weight of the following phosphate group was used as the molecular weight of the hydrophilic group portion. HLB is 3-1
2, preferably 4 to 8. Outside this range, the wettability is undesirably reduced. When the compound C is represented by a general formula,

[0016]

Embedded image (In the formula, n represents an integer of 8 to 18, and m represents 1 or 2.)

Or a salt thereof. More preferred compounds include 2-ethylhexyl acid phosphate, mono- or di-diisodecyl acid phosphate, mono- or di-tridecyl acid phosphate, mono- or di-lauryl acid phosphate, mono- or di-nonylphenyl acid phosphate, and the like. Is mentioned.

The above components may be formulated as a clear coating composition, or they may be blended with a pigment to form a paint. Any type of pigment may be used, but usually, a coloring pigment, an extender pigment, a metal pigment, mica particles and the like are used. Examples of coloring pigments include carbon black, acetylene black, graphite, cadmium yellow, yellow iron oxide, mineral fast yellow, navels yellow, benzidine yellow, molybdenum orange, permanent orange GTR, bengala, cadmium red, resole red, and permanent. Red 4R,
Fast Violet B, Methyl Violet Lake,
Metal phthalocyanine blue, fast sky blue,
Chromium green, chromium oxide, titanium oxide and the like can be mentioned. Examples of the extender include barium carbonate, clay, silica, and talc. Aluminum flake is generally used as the metal pigment. Examples of mica particles include those obtained by enclosing and coating mica particles with a metal oxide, typically, iron oxide or titanium oxide (mica pigment).

The compounding ratio of the component A and the component B is 5 to 60% by weight, preferably 20 to 40% by weight based on the total amount of both components in terms of solid content. 5 crosslinking agents (component B)
If it is less than 10% by weight, curing will be poor and the water resistance will decrease. On the other hand, if it exceeds 60% by weight, the stabilization of the paint will be reduced. The amount of the component C is 0.1 to 5% by weight, preferably 0.5 to 2% by weight, based on the total amount of the components A and B.
% By weight. When the content of the component C is 0.1% by weight, the adhesion, which is an effect of the present invention, is reduced. On the other hand, if it exceeds 5% by weight, the water resistance will decrease.

In the coating composition of the present invention, in addition to the above-mentioned components, additives usually added to coatings, for example, a surface conditioner,
Viscosity suppressants (eg, water-insoluble particles), thickeners, antioxidants, ultraviolet inhibitors, defoamers, and the like may be added. These amounts are within the range known to those skilled in the art.

When the composition of the present invention is applied onto a coating film, the long-chain alkyl group of the component (C) is oriented on the lower coating film, and the wettability of the hydrophobic coating film is improved, so that the lower coating film can be mixed with the lower coating film. We believe that the adhesion is improved.

The production of the paint is not particularly limited, but the component A,
After thoroughly mixing B, add Component C. The coating method of the present composition is diluted with an organic solvent or water to an appropriate viscosity, and spray coating, dip coating, brush coating, etc. are performed.
Dry at 00-200 ° C for 10-60 minutes.

The present invention is particularly excellent as a top coat for automobiles, and is very effective as a base paint for a two-coat one-bake coating system for automobiles. After applying the base paint containing the pigment and applying the clear paint without baking and drying, if a coating defect occurs in the two-coat one-bake coating system where baking and drying is performed, without sanding the defective coating film When a conventionally known base paint is applied and then baked and dried after applying a clear paint, sufficient adhesion between the first base clear paint film and the second base clear paint film cannot be secured. However, when the composition of the present invention is used in a paint, sufficient adhesion can be ensured.

[0024]

EFFECT OF THE INVENTION The coating composition of the present invention has greatly improved adhesion to an undercoat film (the quality of the undercoat film is not taken into consideration), and high interlayer adhesion can be obtained without sanding the undercoat film. Is obtained.

Further, in the case where the composition of the present invention has a defect in the two-coat one-bake coating, the composition of the present invention is added to the second base paint in a coating method in which two-coat one-bake is overlaid again. With the use of, extremely excellent adhesion can be obtained without sanding.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples. The present invention should not be construed as being limited to these embodiments.

Production Example 1 Synthesis of Acrylic Resin 1 76 parts by weight of methoxypropanol was charged into a 2 liter reaction vessel equipped with a stirrer, a temperature controller, and a condenser, and the temperature was adjusted to 12 parts.
It was brought to 0 ° C. Further, 15 parts by weight of styrene, 63 parts by weight of methyl methacrylate, 48 parts by weight of 2-hydroxyethyl methacrylate, 117 parts by weight of N-butyl acrylate, 27 parts by weight of methacrylic acid, 30 parts by weight of acrylamide, 60 parts by weight of methoxypropanol and t-butyl par After a monomer solution comprising 3 parts by weight of oxy-2-ethylhexanate was dropped into the reaction vessel over 3 hours, stirring was continued for 1 hour. Furthermore, dimethylethanolamine 28
And 536 parts of deionized water were added to obtain an acrylic resin having a volatile content of 30% and a resin number average molecular weight of 12,000. The characteristics of this resin were a hydroxyl value of 70 and an acid value of 58.

Production Example 2 (for pigment paste) Synthesis of acrylic resin 2 As in Production Example 1, styrene 24 parts by weight, methyl methacrylate 73 parts by weight, 2-hydroxyethyl methacrylate 48 parts by weight, N-butyl acrylate 117 parts by weight Methacrylic acid, 18 parts by weight of acrylamide, 20 parts by weight of acrylamide, 40 parts by weight of methoxypropanol, and 3 parts by weight of t-butylperoxy-2-ethylhexanate. A polymer was synthesized. Further, 19 parts of dimethylethanolamine and 565 parts of deionized water were added to add 30 parts of volatile matter.
%, An acrylic resin having a number average molecular weight of 12,000 was obtained. The characteristics of this resin had a hydroxyl value of 70 and an acid value of 40.

Production Example 3 Synthesis of Acrylic Resin 3 In Production Example 1, 350 parts by weight of xylene were charged.
℃, glycidyl methacrylate 250 parts by weight,
25 parts by weight of styrene, 60 parts by weight of methyl methacrylate, 165 parts by weight of N-butyl methacrylate and t-
A monomer initiator solution consisting of 50 parts by weight of butyl peroxy-2-hexanoate was added dropwise over 3 hours, and stirring was continued for 2 hours to obtain a nonvolatile content of 55% and a number average molecular weight of 250.
Thus, an epoxy group-containing acrylic resin was obtained.

Production Example 4 Synthesis of Polyester Resin 67 parts by weight of bishydroxyethyl taurine, 65 parts by weight of neopentyl glycol, 118 parts by weight of azelaic acid were placed in a 2 liter reaction vessel equipped with a stirrer, a temperature controller and a cooling pipe.
93 parts by weight of phthalic anhydride and 27 parts by weight of xylene were charged and heated. Water generated by the reaction was removed by azeotropic distillation with xylene.

The temperature is raised to 19 over about 2 hours from the start of reflux.
The temperature was brought to 0 ° C, stirring and dehydration were continued until the acid value equivalent to carboxylic acid became 72.5, and the mixture was cooled to 140 ° C. Then
While maintaining the temperature at 140 ° C., 157 parts by weight of Kadura E10 (manufactured by Shell) was added dropwise over 30 minutes, and then stirring was continued for 2 hours to complete the reaction. Further, 47 parts by weight of dimethylethanolamine were added, and 1100 parts by weight of deionized water were added. The obtained polyester resin had an acid value of 59, a hydroxyl value of 90, a nonvolatile content of 30%, and a number average molecular weight of 105.
It was 4.

Production Example 5 Synthesis of Acrylic Resin The same apparatus as in Production Example 1 was charged with 700 parts by weight of xylene and heated to 130 ° C. 200 parts by weight of styrene, 2-
A monomer initiator solution consisting of 200 parts by weight of ethylhexyl acrylate, 90 parts by weight of hydroxyethyl methacrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of methyl methacrylate and 36 parts by weight of t-butylperoxy-2-hexanoate was dropped in 3 hours, Stirring is further continued for 2 hours, the nonvolatile content is 45%, and the number average molecular weight is 560.
An acrylic resin having 0 and an acid value of 10 was obtained.

Production Example 6 Synthesis of Acrylic Resin The same apparatus as in Production Example 1 was charged with 700 parts by weight of butyl acetate and heated to 130 ° C. 200 parts by weight of styrene, n-
A monomer initiator solution consisting of 200 parts by weight of butyl acrylate, 90 parts by weight of 2-hydroxyethyl methacrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of methyl methacrylate and 36 parts by weight of t-butylperoxy-2-hexanoate is dropped in 3 hours. Then, stirring was further continued for 2 hours, the nonvolatile content was 45%, the number average molecular weight was 8,000,
An acrylic resin having an acid value of 10 was obtained.

Production Example 7 Synthesis of Acrylic Resin The same apparatus as in Production Example 1 was charged with 350 parts by weight of xylene and 350 parts by weight of methoxypropanol, and heated to 130 ° C. 160 parts by weight of styrene, 200 parts by weight of 2-ethylhexyl acrylate, 90 parts by weight of hydroxyethyl methacrylate, 50 parts by weight of methacrylic acid, 100 parts by weight of methyl methacrylate and t-butyl peroxy-2
A monomer initiator solution comprising 36 parts by weight of hexanoate was added dropwise over 3 hours, and stirring was further continued for 2 hours to obtain an acrylic resin having a nonvolatile content of 45%, a number average molecular weight of 5,600 and an acid value of 50.

Production Example 8 Preparation 1 of pigment dispersion paste 54 parts by weight of acrylic resin prepared in Production Example 2, M-11
12 parts by weight of 00 (manufactured by Kablack) and 18 parts by weight of deionized water were mill-dispersed for 3 hours to obtain a pigment paste.

Preparation Example 9 Preparation of Pigment Dispersion Paste 100 parts by weight of the acrylic resin prepared in Preparation Example 6 and 15 parts by weight of Maroon R-6424 (manufactured by Harmon Co.) were similarly mill-dispersed to obtain a pigment paste.

Example 1 Preparation of Water-based Metallic Paint 1 170 parts of acrylic resin of Production Example 1, C-303 (manufactured by Mitsui Toatsu Chemicals, methylated melamine solid content 100%) 21
Part, aluminum paste 7160N (Toyo Aluminum) 1
6.3 parts, lauryl acid phosphate (HLB 7.3)
1.6 parts of a 50% xylene solution was stirred and mixed with a stirrer.

The topcoat composition obtained above was diluted with deionized water, and the viscosity was adjusted at 20 ° C. for 30 seconds with a Ford cup # 4 to obtain an aqueous metallic paint.

Example 2 Preparation of water-based paint 2 170 parts of the above acrylic resin of Production Example 1, C-303 (manufactured by Mitsui Toatsu Chemicals, methylated melamine, solid content 100%)
30 parts, 30 parts of the M-1100 pigment paste of Production Example 8,
2.5 parts of a 50% xylene solution of stearyl acid phosphate (HLB 5.5) was stirred and mixed with a stirrer.

The top coating composition obtained above was diluted with deionized water, and the viscosity was adjusted with a Ford cup # 4 at 20 ° C. for 30 seconds to obtain an aqueous coating composition.

Example 3 Preparation of Solvent-Based Paint 3 150 parts of acrylic resin of Production Example 6, U-20N-60
(Mitsui Toatsu Chemicals, butylated melamine), 17 parts of Bright Copper (Mica, Marl), 18 parts of Perind Maroon R6424 pigment paste of Production Example 9, 50% xylene of isostearyl acid phosphate (HLB 5.5) 3.2 parts by weight of the solution was stirred and mixed with a stirrer.

The acrylic melamine-based paint obtained above was diluted with a 1: 1 mixture of ethyl acetate and xylene, and the viscosity was adjusted at 25 ° C. for 30 seconds in a Ford cup # 4 to obtain an acrylic melamine-based paint.

Example 4 Preparation of water-based paint 4 180 parts of the polyester resin of Production Example 4, C-303 (manufactured by Mitsui Toatsu Chemicals, methylated melamine solid content 100%) 2
5 parts, M-1100 pigment paste of Production Example 1 16.3
Part, 5 of lauryl acid phosphate (HLB7.3)
2.5 parts of a 0% xylene solution was stirred and mixed with a stirrer.

The top coating composition obtained above was diluted with deionized water, and the viscosity was adjusted at 20 ° C. for 30 seconds with a Ford cup # 4 to obtain an aqueous coating composition.

Example 5 Preparation of water-based metallic paint 5 170 parts of acrylic resin of Production Example 1, U-20N-60
(Mitsui Toatsu Chemical Co., butylated melamine) 20 parts, 10 parts of a blocked isocyanate compound obtained by blocking isophorone diisocyanate with methyl ethyl ketone oxime,
Aluminum paste 60-600 (made by Toyo Aluminum) 1
6.3 parts, 2-ethylhexyl acid phosphate (H
2.4 parts of a 50% xylene solution of LB 9.2) was stirred and mixed with a stirrer.

The topcoat composition obtained above was diluted with deionized water, and the viscosity was adjusted with a Ford cup # 4 at 20 ° C. for 30 seconds to obtain an aqueous metallic paint.

Production Example 10 Preparation of Clear Paint 1 80 parts of the acrylic resin of Production Example 5 and 15 parts of U-20N-60 (butylated melamine, manufactured by Mitsui Toatsu Chemicals, Inc.) were stirred and mixed with a stirrer.

The acrylic melamine clear paint obtained above was diluted to a 1: 1 mixture of Solvesso 100 and Solvesso 150, and the mixture was heated at 20 ° C. in a Ford cup # 4.
The viscosity was adjusted for 22 seconds to obtain an acrylic melamine-based clear paint.

Production Example 11 Preparation of clear paint 3 500 parts of the acrylic resin of Production Example 7, 100 parts of the epoxy group-containing acrylic resin of Production Example 3, and 7 parts of a 20% methanol solution of tetrabutylammonium bromide were stirred and mixed with a stirrer. did.

The acid-epoxy-cured clear coating obtained above was applied to Solvesso 100 and Solvesso 150:
Dilute to 1 mixture, 2 in Ford Cup # 4 at 20 ° C
The viscosity was adjusted to 2 seconds to obtain an acid epoxy clear paint.

Production Example 12 Preparation 4 of clear coating material 50 parts of the acrylic resin of Production Example 5, 20 parts of C-303 (manufactured by Mitsui Toatsu Chemicals, methylated melamine solid content 100%),
Blocked isocyanate compound 2 in which isophorone diisocyanate is blocked with methyl ethyl ketone oxime
0 parts, dibutyltin dilaurate 5% xylene solution
Six parts were stirred and mixed with a stirrer.

The acrylic-melamine-isocyanate-based clear coating obtained above was diluted with Solvents 150, and the viscosity was adjusted with a Ford cup # 4 at 20 ° C. for 22 seconds to obtain an acrylic-melamine-isocyanate-based clear coating.

Comparative Example 1 An aqueous metallic paint was obtained by adding ethyl acid phosphate (HLB value: 15.4) in place of lauryl acid phosphate in Example 1.

Comparative Example 2 Lauryl polyoxyethyl acid phosphate (HLB) was used in Example 1 in place of lauryl acid phosphate.
Value 12.1 (n = 4) and HLB value 13.5 (n =
6)) was added to obtain an aqueous paint.

Comparative Example 3 In place of lauryl acid phosphate in Example 1, 1.6 parts of a reaction product of a bisphenol A type epoxy resin having a molecular weight of 400 and phosphoric acid were added to obtain an aqueous paint.

Comparative Example 4 In Example 1, 0.16 parts by weight of a 50% xylene solution of lauryl acid phosphate was added to obtain an aqueous paint.

Comparative Example 5 In Example 1, 16 parts by weight of a 50% xylene solution of lauryl acid phosphate was added to obtain an aqueous paint.

Example 6 Method for Forming Coating Film The coating material obtained in Example 1 was air-sprayed on a non-sanded intermediate-coated steel sheet so as to have a dry coating film thickness of 15 μm. After preheating for minutes, the clear paint obtained in Production Examples 10 to 12 was air-sprayed so as to have a dry film thickness of 40 μm, and after setting for 7 minutes, dried at 140 ° C. for 20 minutes. The adhesion of the coating film was evaluated. Table 1 shows the results of the combination of the base coating and the clear coating and the adhesion.

Table 1 Test plate base paint Clear paint adhesion * 1 Example 1 Production Example 10 100/100 2 Example 2 Production Example 10 100/100 3 Example 3 Production Example 10 100/100 4 Example 4 Production Example 11 100/100 5 Example 5 Production Example 12 100/100 6 Comparative Example 1 Production Example 12 5/100 7 Comparative Example 2 Production Example 12 8/100 8 Comparative Example 3 Production Example 12 8/100 9 Comparative Example 4 Production Example 12 10/100 10 Comparative Example 5 Production Example 12 10/100 *: Cuts were made at intervals of 2 mm with a cutter knife to make 100 cuts of 2 mm square, and a peeling test using a tape was performed. Numerical values indicate the number of unpeeled / 100.

Example 7 Method for forming a coating film Base paint prepared in Examples 1 to 5 and Comparative Examples 1 to 5 on a medium-coated steel sheet, and then a clear coating material of Production Examples 10 to 12 were dried by a dry coating film, the former having a thickness of 15 μm and the latter having a dry coating film. Paint the former to 40 microns, then set for 5 minutes, 80
At 5 ° C. for 5 minutes, then apply the latter,
Setting was performed for 0 minutes. The coated plate is dried at 160 ℃,
A test plate was prepared by baking for 18 minutes.

The same base paint and clear paint were repainted again without sanding the test plate.
Baking was performed at 40 ° C. for 18 minutes to form a two-coat one-bake coating film composed of four layers. The recoat adhesion of this coating film was evaluated. Table 2 shows the results of the combination of the base coating and the clear coating and the recoat adhesion.

Table 2 Test plate base paint clear paint recoat adhesion * 1 Example 1 Production Example 10 100/100 2 Example 2 Production Example 10 90/100 3 Example 3 Production Example 10 90/100 4 Example 4 Production Example 11 98/100 5 Example 5 Production Example 12 95/100 6 Comparative Example 1 Production Example 12 5/100 7 Comparative Example 2 Production Example 12 5/100 8 Comparative Example 3 Production Example 12 8/100 9 Comparative Example 4 Production Example 12 15/100 10 Comparative Example 5 Production Example 12 12/100 *: Cuts were made at intervals of 2 mm with a cutter knife to make 100 cuts of 2 mm square, and a peeling test using a tape was performed. Numerical values indicate the number of unpeeled / 100.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a multilayer coating film according to the related art and the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Manabu Yoshioka 19-17 Ikedanakamachi, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Inventor Hiroshi Miwa 19-17 Ikedananakacho, Neyagawa-shi, Osaka Japan Paint (56) References JP-A-1-188571 (JP, A) JP-A-61-166863 (JP, A) JP-A-57-87869 (JP, A) JP-A-3-95275 (JP, A) JP-A-2-173173 (JP, A) JP-A-62-184071 (JP, A) JP-A-57-172 (JP, A) JP-A-54-95637 (JP, A) (58) (Int.Cl. ⁷ , DB name) B05D 1/00-7/26 C09D 5/00-201/10

Claims (4)

(57) [Claims] 1. A cured coating film comprising a first base coat and a first clear coat formed on the first base coat is formed on a substrate, and a second cured coating film is formed without sanding the cured coating film. A second base coat and a second clear coat without curing the second base coat, and then baking and curing both the second base coat and the second clear coat. And the second base coat has (A) a film-forming resin, (B) a crosslinking agent for heat-curing the resin (A), and (C) a long-chain alkyl group having 8 to 18 carbon atoms, and H
Interlayer adhesion containing a phosphate ester having LB 3 to 12, wherein the solid content of the component (C) is 0.1 to 5% by weight based on the total solid content of the components (A) and (B). A method for forming a coating film comprising a coating composition having improved properties. 2. The method according to claim 1, wherein the film-forming resin (A) is an aqueous resin having an amide group. 3. The method according to claim 1, wherein said component (A) comprises 5 to 40% by weight of an amide group-containing ethylenic monomer, 3 to 25% by weight of an acid group-containing ethylenic monomer and another polymerizable ethylenic monomer. The method according to claim 1, which is an acrylic resin prepared. 4. A multilayer coating film obtained by the method according to claim 1.